1. Field of the Invention
The present invention relates to an optical disk reproducing apparatus having a vibration detecting device capable of measuring an amplitude of vibrations caused by mass eccentricity of an optical disk.
2. Description of the Related Art
In recent years, the recording and reproducing speed of an optical disk reproducing apparatus has been remarkably enhanced. In the optical disk reproducing apparatus, the reproducing speed has been enhanced by increasing the rotational speed of the optical disk.
However, when the rotational speed of an optical disk is increased, vibrations caused by mass eccentricity of the optical disk have adverse effects on the control of a servo and the like, which gives disagreeable feelings to a user of an optical disk reproducing apparatus. In order to prevent or reduce adverse effects of the vibrations caused by an optical disk having large mass eccentricity, when such an optical disk is mounted, an optical disk reproducing apparatus limits the rotational speed thereof. The measurement of the amplitude of vibrations is an important technique for assisting in preventing adverse effects of the vibrations caused by an optical disk having mass eccentricity in an optical disk reproducing apparatus.
FIG. 6 is a block diagram of a conventional optical disk reproducing apparatus 600. Reference numeral 1 denotes a base, 2 denotes a disk motor attached to the base, 1, 3 denotes an insulator supporting the base 1, 4 denotes an optical disk attached to the disk motor 2, 21 denotes an acceleration sensor attached to the base 1, and 22 denotes a measurement portion for determining an amount of mass eccentricity, based on an output from the acceleration sensor 21.
When the disk motor 2 is rotated at a predetermined velocity, centrifugal force which is proportional to an amount of mass eccentricity of the optical disk 4 is generated. The base 1 supported by the insulator 3 vibrates at an amplitude determined by the amount of mass eccentricity of the optical disk 4, the entire mass of the base 1 and components mounted thereon, and the spring constant of the insulator 3.
The vibrations of the base 1 are converted into an electrical signal by the acceleration sensor 21. The measurement portion 22 measures the amplitude of the vibrations of the base 1 based on the electrical signal converted by the acceleration sensor 21.
However, in the above-mentioned optical disk reproducing apparatus 600, the acceleration sensor 21 and a signal amplifier (not shown) for amplifying a signal from the acceleration sensor 21 are provided, which increases cost.
Furthermore, space is required for mounting the acceleration sensor 21 and the signal amplifier.